the Gram staining reaction fermentative metabolism of glucose and production of

The gram staining reaction fermentative metabolism of

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the Gram-staining reaction, fermentative metabolism of glucose, and production of arginine dihydrolase, catalase and oxidase, but not of lysine or ornithine decarboxyl- ase. Caution is advocated should consideration be given to using commercially available diagnostic kits. The API 20E (Figure 6.35 [see colour section]) and API- zym (Figure 6.36 [see colour section]) systems, and more recently the API 20NE API 50CH, API 50L, Biolog-GN, Enterotubes and RapidID 32 systems (Meyer and Bullock, 1973; Amandi et al., 1982) have made an inroad into routine diagnostic laboratories. Whereas some systems, e.g. Biolog-GN, are clearly adaptable to and useful for environmental isolates, others have been developed specifically for a given use, usually medically important bacteria. The consequence is that the supporting identification schemes may be inappropriate. Many workers have used the API 20E system for the identification of fish-pathogenic bacteria, and the technique has been considered useful be some (e.g. Santos et al., 1993). For example, by inference the API 20E rapid identification system may be useful for diagnosing Flavobacterium sp. (Acuigrup, 1980a). Kent (1982) reported that V. ordalii produces a characteristic profile in API 20E, i.e. Kent (1982) reported the API 20E profile for V. anguillarum as: + v + V + + + + - + - + - + V + whereas Maugeri et al. (1983) published a slightly different pattern, i.e. v + — — V — — — V V vH—h — — — V — + V + where "v" indicated a variable result. Kent (1982) reported that Ph. damselae subsp. piscicida gave positive responses in the API 20E rapid identification system for arginine dihydrolase and weak acid production from glucose, all other tests being negative. Of course, it is necessary to modify the protocol for use with marine bacteria. Thus, it was essential to suspend cultures in 2-3% (w/v) saline rather than distilled water, and the inoculated test strips were incubated at 25°C (not 37°C) for up to 48 h. Maugeri et al. (1983) considered that it was essential to carry out some additional tests with putative V. anguillarum, namely motility and sensitivity to 0/129, in order to confirm that the isolates were indeed motile and were inhibited by the vibriostatic agent. However, some cultures may be resistant to the action of 0/129 (Muroga et al, 1979) and appear to be non- motile. The latter phenomenon may result from exposure to the partial inhibitory activity of some antimicrobial compounds. The API 20E system weighs heavily on the use of sugar fermentation reactions, which may be influenced by the presence of plasmids. The profile(s) for Aer. hydrophila are similar to those of Aer. allosaccharophila and Aer. sobria, whereas T. maritimum and Ps. anguilliseptica may be indistinguishable by the API 20E rapid
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216 Bacterial Fish Pathogens identification system. Y. ruckeri may be confused with Haf. alvei. Toranzo et al.
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